tools lib api fs: Adopt filename__read_str from perf

We already moved similar functions in here, also it'll be useful for
sysfs__read_str addition in following patch.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1455465826-8426-3-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 53 insertions, 0 deletions

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 459599d1b6c4..2cbf6773ca5d 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -13,6 +13,7 @@
 #include <sys/mount.h>
 
 #include "fs.h"
+#include "debug-internal.h"
 
 #define _STR(x) #x
 #define STR(x) _STR(x)
@@ -300,6 +301,56 @@ int filename__read_ull(const char *filename, unsigned long long *value)
         return err;
 }
 
+#define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
+
+int filename__read_str(const char *filename, char **buf, size_t *sizep)
+{
+        size_t size = 0, alloc_size = 0;
+        void *bf = NULL, *nbf;
+        int fd, n, err = 0;
+        char sbuf[STRERR_BUFSIZE];
+
+        fd = open(filename, O_RDONLY);
+        if (fd < 0)
+                return -errno;
+
+        do {
+                if (size == alloc_size) {
+                        alloc_size += BUFSIZ;
+                        nbf = realloc(bf, alloc_size);
+                        if (!nbf) {
+                                err = -ENOMEM;
+                                break;
+                        }
+
+                        bf = nbf;
+                }
+
+                n = read(fd, bf + size, alloc_size - size);
+                if (n < 0) {
+                        if (size) {
+                                pr_warning("read failed %d: %s\n", errno,
+                                         strerror_r(errno, sbuf, sizeof(sbuf)));
+                                err = 0;
+                        } else
+                                err = -errno;
+
+                        break;
+                }
+
+                size += n;
+        } while (n > 0);
+
+        if (!err) {
+                *sizep = size;
+                *buf   = bf;
+        } else
+                free(bf);
+
+        close(fd);
+        return err;
+}
+
 int sysfs__read_ull(const char *entry, unsigned long long *value)
 {
         char path[PATH_MAX];
diff --git a/tools/lib/api/fs/fs.h b/tools/lib/api/fs/fs.h
index d024a7f682f6..858922b61141 100644
--- a/tools/lib/api/fs/fs.h
+++ b/tools/lib/api/fs/fs.h
@@ -2,6 +2,7 @@
 #define __API_FS__
 
 #include <stdbool.h>
+#include <unistd.h>
 
 /*
  * On most systems <limits.h> would have given us this, but  not on some systems
@@ -26,6 +27,7 @@ FS(tracefs)
 
 int filename__read_int(const char *filename, int *value);
 int filename__read_ull(const char *filename, unsigned long long *value);
+int filename__read_str(const char *filename, char **buf, size_t *sizep);
 
 int sysctl__read_int(const char *sysctl, int *value);
 int sysfs__read_int(const char *entry, int *value);